Electrical control circuit



,May 2s, 19:55.

E.-o. ERlcKsoN ELECTRICAL CONTROL CIRCUIT Filed `May 15, 1933 co'nnmwx nennen SISTRHCE Jhonny;

Patented May ze, 193s UNITED STATES PATENT oFFicE ELECTRICAL CONTROL CIRCUIT Ellis Osmon Erickson, Pasadena, Calif., assignor to Claude'Neon Electrical Products Corporation, Ltd., Wilmington, Del., a corporation of Delaware Application May 15, 1933, Serial No. 671,055-

9 claims. (ci. '11s-124) This invention relatesbroadly to the control of potentials in electrical circuits and has a particular application to the dimminggof electric lamps and the ilashing of gaseous discharge devices, such as neon lamps. It is particularly useful for ilashing purposes in connection with gaseous discharge lamp systems of the type disclosed in my copending application Serial No. 664,191, filed April 3, 1933, entitled Neon lamp circuit, in which a special means is employed for starting the lamps. A broad object of the invention is to vary the potential in a circuit carrying considerable kpower under the control of a circuit carrying only a relatively small amount of power without resorting to the use of relays or-other devices having con; tacts in the power circuit.

Another object is to provide a transformer construction having power circuit windings capable of handling considerable power, and a. control winding that needs handle only relatively small .amounts of power for varying the output potential of the transformer throughl a wide range.

Another object of the invention is to extinguish the arc in a gaseous discharge device without rent of substantial magnitude or at substantial potential, and without imposing excessive current upon any element of the lamp circuit.

Another object is to provide a very simple and effective method of flashing gaseous discharge lamps that are provided with starting equipment of the type disclosed in my aforementioned api plication Serial No. 664,191.

The application of the invention lin connection with the ashing of gaseous discharge lamps may l be briefly described as follows:

The gaseous discharge lamps most commonly used comprise elongated tubes filled with suitable gases at suitable pressure and having electrodes at opposite ends for supplyingfcurrent to the gas column. yThese lamps, in operation, have negative resistance characteristics and for' that reason are supplied vwith current from a circuit having substantial inductive reactance for regulation purposes. The regulating reactance may consist of a reactance element connected directly in series with the lamp, this arrangement being generally used when the lamp is operated at potentials less than the available line potentials; or it may be constituted by the leakage reactance of a transformer used to couple the'lamp to the line, 'the latter arrangement being commonlyv employed when the lamp requires a potential greater than line potential.

There are several obvious ways Aof interruptmaking or breaking a circuit carrying any cur' ing the flow of current through a gaseous discharge'lamp in a circuit of the type described. One way is to open the supply circuit, but this entails the use of switch contacts capable of handling the total power delivered to the lamp and 5 is objectionable for that reason.

Another way is to short-circuit'the lampbut this' is objectionable because the regulating reactance element in series withrthe lamp must then be designed to withstand full line potential; fur- 10 thermore, the switch contacts must be capable of handling currents in excess of the normal lamp current. This method also wastes power due to the losses in the reactance element and imposes a load of low power factor on the line.

A third method would be to introduce an impedance in series with the lamp to reduce the lamp current to such a point that the lamp would not operate. However, the actual introduction of such an impedance in conductive relation in the .20 circuit would involve diiiiculties.

In accordance with the present invention, I introduce an impedance in series with the lamp to reduce the current in the lamp below a value sumcient to maintain the discharge by inductively 25 coupling an impedance to the lamp circuit instead of conductively connecting it thereinto. In this manner the lamp may be extinguished without actually breaking the power circuit of the lamp.

My new method lends itself admirably to the 3o lamp-starting circuits of my application Serial No. 664,191, because those circuits are already provided with coils inductively coupled to the lamp supply circuits, which coils may be used i'or inductively introducing an extinguishing impeda5 ance into the supply circuit. Specic applications of the invention to gaseous discharge lamp circuits will be described in detail following the analysis of the general circuitjnvolved.

In the drawing:

Figure 1 is a schematic circuit diagram of a transformer for supplying current to a load circuit with a special control winding on the transformer for varying the potential applied to the load;

Figure 2 is a schematic circuit diagram of a t system incorporating the invention for dashing a gaseous discharge lamp;

Figure 3 is a schematic circuit diagram of a control system for a lamp energized directly from a pair of line terminals in series with a regulating reactance; and

Figures 4 and 5 are graphs explaining the operation of the circuit shown in Figure 1.

Referring toFigure 1, I have shown a trans- Il magnetic core upon opposite legs of which are mounted a primary winding 4 and a secondary winding 5, and having a shunt core section upon which is mounted a tertiary winding 3 for control purposes. The primary winding 4 is designed to be connected to a source of alternating current 8 and the secondary winding 5 is adapted to be connected through a switch. 50 to a load circuit indicated diagrammatically as an impedance 6. The tertiary winding 3 is shown connected to a variable impedance element 1.. The load impedance 6 may consist predominantly of resistance and the control element may consist of a resistance, a reactance, a capacitance, or a combination of such elements.

For convenience in describing the operation of. the transformer I, the core section is divided by dotted lines into three sections, a, b, and c, respectively; It will be observed that the core sections a and b form a closed magnetic circuit, upon opposite legs of which the primary and secondary windings 4 and 5, respectively, are mounted and that the shunt core section c, together with the air gap d, constitute a magnetic path in shunt to the respective magnetic paths comprising core sections a and b upon which the primary and secondary windings are positioned. l Because of the relatively high reulctance of the air gap d the shunt path comprising the core section c and the air gap d in series offers a substantially higher reluctance than the closed magnetic circuit comprising core sections a and b; therefore, when the secondary winding 5 is not drawing current (as.

when switch 50 is open) the major portion of the total flux developed in core section a by the magnetizing current in the primary winding 4 threads the core section b. Under the conditions outlined, the flux ilowing through the core section c across the air gap d may comprise -only 10 per cent or less of the total flux developed in the core section a.

However, when the switch is closed to connect the load impedance 6 across the secondary winding 5, current iiows in the secondary winding 5 and the direction of this current is such as to develop, or tend to develop, in the core section b a magnetic iiux opposing the' flux developed by the primary winding 4. Under these conditions, a substantial ilux is developed in the'shunt core section c and this, in effect, introduces substantial leakage reactance eiectively in series with the secondary winding 5-so that the potential applied to the load impedance 6 is substantially less than the open circuit potential of the secondary winding 5.

Transformers of the general type described, having a\shunt core section, are old in the art and have been used extensively for supplying loads such as neon lamps which require a regulat-ing reactance in series with the load. 'However to the best of my lgrnowledgain the prior known constructions there was no way of varying the amount of leakage reactance introduced effectively in series with the secondary winding except by changing the structure of the transformer, as for instance by varying the length of the shunt core section c to increase or decrease the length of the air gap d and thereby vary 'the total reluctance of the shunt magnetic path. l

In accordance with the present invention, I

have discovered that an eiect substantially- $3,002,769v former designated generally at 1, having a vclosed shunt core section c and connecting the terminalsl of the tertiary winding to an impedance of specific characteristics. Thus I have discovered that if the load 6. is substantially resistive the current delivered to the load may be increased by employing a device having predominantly inductive reactance, as the element 1, the inductive load across the tertiary winding 3, in effect, increasing the air gap d and decreasing the leakage 'reactance of the transformer. If the impedance element 1 is capacitative a substantially dierent result is obtained, a Very low capacitive reactance producing an increase in the output current of the transformer over 'that resulting when the winding 3 is open circuited, whereas higher capacitive reactance produces marked reductions in theoutput current as compared to the current supplied with the winding 3 open circuited. The general relation between transformer output current (when supplying a constant resistive load) anddiierent pure reactance values for the impedance 1 shunted across the tertiary winding is shown by the curves of Figure 4 in which the ordinates represent current i'low in amperes and the abscissai represent the reactance in ohms of the impedance 1. In Figure 4 the ordinate of point represents the magnitude of the output current when the tertiary winding 3 is short cir'- cuited (corresponding .to zero value -for impedance 1) and the ordinate of the horizontal dotted line 6| represents the magnitude of the output current when the tertiary winding 3 is open circuited (corresponding to infinite value for impedance 1) It will be observed that the curves for inductively reactive and capacitivel'y reactive 'control impedances (impedance 1) assymptotically approach the li 6l. It will also `be observed that for various values of inductive reactance the output current is always greater than that obtained when the tertiary winding is open'circuited (the line 6I), and varies relatively gradually with changes in the' reactance. On the other hand, when the element 1 is capacitively reactive the output current changes rapidly and except for very low values of reac tance the output current is less than the current (line 6l) when the tertiary winding is open circuited. Obviously, when utilizing a capacitive reactance it is desirable to so proportion it as to utilize the sharply falling portion of the curve for reducing the transformer output current.

'I'he curve of Figure 5 shows the relation between transformer output current to a resistive symptotically toward the open circuit value. Al-

though the current curve far a pure resistance tertiary coil loading shows what might. be considered very littlecontrol effect over any useful range, it actually is sufficient when the loadI 6 comprises a gaseous discharge tube or lamp to reduce the current in the tube suiciently to extinguish the tube.

An importantvadvantage of the circuit shown in Figure 1 is that the control impedance element 1 may be located at a point remote from the transformer l. Furthermore, I have discovered that the tertiary winding 3 andthe control impedance 1 may be designed to be built at low consumed by the load impedance 6, which power must, of course, be handled by the primary and secondary windings 4 and 5, respectively.

`Referring now to Figure 2, I have shown a gaseous discharge lamp I6 having a pair of electrodes. II and I2, respectively, adapted to be heated from any convenient source of current. The electrode II is shown connected to one conductor I3 of a three-wire supplycircuitwhich may provide a potential of 220 volts between the two outside conductors I3 and I5 and a potential of 110 volts between either of the outside conductors and a neutral conductor I4. The other terminal I2 of the lamp I9 is connected to one end of a. high potential secondary winding I6 of a transformer I1. Transformer I1 is of the type previously described in connection with Fig. l having, in addition to the secondary winding I6, a primary winding I8 and a tertiary winding I9 on a shunt core section lof the transformer. The primary winding I6 is connected across the line conductors I4 and I5, as shown, and the opposite end of the secondary winding I6 is also connected to the line conductor I5 so that the total potential impressed upon the lamp I0 is the sum of the line potential between the line conductors I2 and I5 and the potential developed in the secondary winding I6.

The lamp I0 is of a type that is incapable of automatically starting in response to application of the normal operating potential thereto. For this reason, a starting device is provided for initiating a discharge in the lamp. This starting device may comprise a spark coil adapted to be energized by a 110-volt current and to produce a high frequency discharge which is applied over a conductor 2l to an electrode 22 positioned adjacent the lamp I0. Starting devices of this type are old and well-known in the art, and need not be described in-detail herein.

The spark coil 26 is provided with energizing potential .by connecting one of its input terminals'to the junction point 23 of a reactance element 24 and a resistance element 25 connected in series across the line conductors I3 and I5; and connecting the other input terminal through a switch contact 26, a switch arm 21 and the tertiary winding I9 to conductor I5. L

A second switch contact 26 is connected through an impedance element 2 9 (corresponding in function to the impedance element 1 in Figure 1) to that end of the tertiary winding I9 which is connected to the line conductor I5.

The circuit described functions as follows: Assume that the switch arm 21 is in mid position out of engagement with both contacts 26 and 26 and that the line conductors I2, I4 and I5 are energized. Under these conditions, the secondary winding I6 of the transformer I1 will develop its full open circuit potential and this potential will be applied in'series with the line potential tained at a substantially constant potential different from the potential of conductor I6 by a substantial amount, and out of phase therewith. This constant potential developed at the junction point 22 is-constantly applied to one input' terminal of the starting device 26. With the switch arm 21 closed upon contact 26, the other input terminal of the starting device 20 is connected through the tertiary winding I9 to the line conductor I5. Because of the fact that, with the lamp I0 not operatingthe secondary wind- Ving I6 of the transformer isdrawing no current, only a very small portion of the flux developed in the transformer core by the primary winding I8 passes through the shunt core section. Therefore, when the lamp isnot operating, only a negligible potential is developed in the tertiary winding I9 and the potential applied through the contact 26 to the input terminal of the starting device 20 is substantially that of the line conductor I5. Therefore, substantial potential is applied to the input terminals of the starting device 20 and the latter is actuated to develop high frequency impulses which are applied to the electrode 22 and start the discharge in the lamp I0.

Of course, as soon as thelamp I9 begins to operate, it draws current from the secondary winding I6 of the transformer and the current flow in winding I6 tends to produce a flux opposing that produced by the primary winding I8 with the result that a substantial flux is produced in the shunt core section upon which the tertiary winding I9 is positioned. Therefore, with the lamp operating, a substantial potential is developed in the tertiary winding I9 and. this winding is so dimensioned and poled as to produce at the input terminal of the starting device 20 connected thereto through contact 26, a potential substantially equal in phase and magmtude to the potential of the junction point 23. Therefore, the starting device ceases to function as soon as the lamp III starts operation. Circuits of the general type described, including a tertiary winding. on the la-.mp transformer for controlling the operation of the starting device, are fully discussed in my copending application, SerialNo. 664,191, previously referred to, and a full explanation of the theory of operation of such cir-.. cuits for starting purposes is given therein.

When it is desired to extinguish the lamp I6, the switch arm 21 isthrown from contact 26 to contact 28.Y This connects the impedance 29, which may comprise either a capacity reactance element or a resistance element, directly in shunt to the tertiary winding I9 and has the eiIect of decreasing the output current fromwinding I6 of the transformer in the manner previously described in connection with Figure 1.v This decrease in current reduces the total current supplied to thelamp I6 and by suitably proportioning the impedance element 29 relative to the tertiary winding I9 the reduction in the current may be made of sulcient magnitude to extinguish the lamp I0.A Immediately the lamp is extinguished, it ceases to draw current from the secondary winding I6 and this. in turn, reduces the flux in the shunt core of the transformer to its original value and, of course, decreases me potential developed in the tertiary winding I9 to a negligible value so that if desired the switch arm 21 may be left against contact 26 'without producingany appreciable energy loss in the ter.- tiary winding I9 and the impedance element 29, or the contacts may be broken without appreciable sparking because of the low voltage developed. Y

It will be observed from the foregoing description that the lamp Il may be started at will by shifting theswitch arm 21 into engagement with contact 26 and extinguished by shifting the switch arm into engagement with contact 28. Obviously, if desired, the switch arm 21 may be constituted by the armature of a relay or by any automatic mechanical switching device for closing the two circuits alternately at any desired intervals to automatically ash the lamp l0.

The system of Figure 2 just described related to the operation of a lamp requiring potential greater than line potential, in which case the necessary high potential could only be obtained by the use of a transformer. In AFigure 3 my invention is shown applied to the flashing of a lamp which is capable of voperating at potentials less than line potentials. In Figure 3 I have shown a lamp 30 having a pair of electrodes 3l and 32, respectively, adapted tobe heated from any desired source of current and connected inseries with the winding 33 of a regulatingv reactance across line conductors 34 and 35. In this instance, the regulating reactance is provided solely for controlling the flow of current through the lamp 30 Whenthe latter is operating, such a controlling impedance in series with the lamp being required because 'of the negative resistance characteristic vof the lamp. A starting device 36 is provided for starting the lamp 30 and has a pair of input terminals connected respectively to a contact 31 and the junction point 38 of a reactance element 39 and resistance element 40 connected inseries across the line conductors 34 and ,35. A switch arm 4 i, adapted to be moved into and out of engagement with the contact 31, is connected to one end of an auxiliary winding 42 on the same core as the winding 33 and closely coupled thereto. The other end of winding 42 is connected to line conductor 34 and is also connected through a control impedance 43, which is either capacitively reactive-or resistive, to the vother contact 44 associated with the switch arm The circuit of Figure 3 functions substantially the same as that of Figure 2. Thus, when the switch arm 4I is moved into engagement with contact 31 substantial voltage is supplied to the starting device 36 because of the fact that the junction point 38 is at a potential substantially different from the potential of line 34, whereas the switch arm 4i is then substantially at the vsame potential as line 34 because of the fact that the lamp 30 is drawing no current through winding 33 and, therefore, no potential is induced in the auxiliary winding 42. When the lamp starts, it immediately draws current through the winding 33 of the regulating reactance and this flow 444, thereby connecting the control impedance 43 across the winding v42. I have found that the effect of connecting the capacitively reactive or resistive impedance 43 across the winding 42 is to increase the impedance of the winding 33 and by. suitably proportioning the impedance element 43 the effective impedance of winding 33' may be increased suiliciently to decrease the current in the lamp below the value necessary to' support the arc, whereupon the lamp is extinguished. With the lamp extinguished, the current in winding 33 falls to zero. This is a desirable feature because it'means that the impedance element 43 need be designed to handle only currents of very shortl duration. l Furthermore, when the switch arm 4l is subsequently moved from contact 44 to contact 31 to again start the lamp 30, there is no arc at contact 44 since no current is flowing in its circuit at that time. A

Numerous variationsin' the specific circuit shown may be introduced without departing from the essential principles disclosed, and the invention is, therefore, to be limited only as set forth in the appended claims.

I claim:

1. In combination, a source of A. C. potential; a non-self-.starting gaseous discharge device having high impedance when not operating, a lower impedance when operating, and requiring current 'in excess of a predetermined value to maintain it in operation; means for supplying operating current from said source to said discharge device comprising a' transformer having iirst and second core sections constituting a closed magnetic circuit of low reluctance, and a. third core constituting a magnetic circuit of relatively high y lsecond core section vhaving a secondary winding thereon connected to said discharge device, and said third core section having a control winding thereon; and a switch and impedance element connected in series withsaid control winding for A decreasing the current supplied to said discharge device below said predetermined value in response to closure of said switch.

2. In combination, a source of A. C. potential; a non-self-starting gaseous discharge device having high impedance when not operating, a lower impedance when operating, and requiring current in excess of a predetermined value to maintain it in operation; means comprising an inductive winding in series with said device for supplying operating current to said device from said source; a terminal, and means connected to said source for deriving therefrom a substantially constant reference potential andapplying it to said terminal; a control winding inductively coupled to said rst Winding. and connected at one end to one side of said source, said control winding being so proportioned and poled as to have induced therein, when said gaseous discharge device is drawing operating current through said inductive winding, a potential substantially equal to said reference potential; a starting device having inputterminals for initiating a discharge in said gaseous discharge device in response to potential'applied 'to its input terminals; an impedance element; and switch means for alternately connecting said impedance element in shunt'to said control winding to revice below said predetermined value, and connecting the input terminals of said' starting device between the free end of said control winding and said terminal to start said discharge device.

3. A system as described -in claim 2 in which said means for deriving the reference potential of constant value comprises a reactance element and a resistance element connected in series across said. source. andsaid terminalis connected 65 duce the current supplied to said discharge dey 2,002,769 to the junction between the reactance element and resistance element. A

4. In combination, a source of A. C. potential; a non-self-starting gaseous discharge device having high impedance when not operating, a. lower impedance when operating, and requiring current in excess of a predetermined Value to main` :tain it in operation; means comprising an inductive winding connected in series with said device across said source of potential for supplying operating current 'to said device from vsaid source; a control windinginductively coupled tov said first winding` and connected at one end to one side of said source, said control winding' being so proportioned and poled as to have induced therein, when said gaseous discharge device is drawing operating current through said inductive Winding, a potential substantially equalto said reference potential; a starting devicehaving input terminals fori'initiating a discharge in said gaseous discharge device in response to ptential applied to its input terminals; an impedance element; and switch means for alternately connecting said impedancel elementin shunt to said control winding to reduce the current supplied to said discharge device below said predetermined value,` and connecting the input terminals of said starting device between the free end of said control winding and said terminal having the constant potential applied thereto, to start said discharge device.

5. In combination, a source of A. C. potential, a non-self-starting gaseous discharge device having high impedance when not operating, a lower impedance when operating,.and requiring current in excess of a predetermined value to maintain it in operation; means forI supplying operating current from said source to said discharge y device comprising a' transformerv having rst and second core sections constituting a closed magnetic circuit of low reluctance, and a third core section constituting a magnetic circuit of rela- 'tively high reluctance in shunt to said firstand and said thirdl core 4section having a control wind-.-

ing thereon; a terminal, and means connected to said source for deriving therefrom a substantially constant reference potential and applying to said terminal; said control winding being connected at one end to one side of said source and Abeing so proportioned and poled as tohave induced therein, when said gaseous dischargev device is drawing operating current from the secondary winding of said transformer, a potential substantially equal 'to said reference potential; a starting device having input terminals for initiat- 'ing a discharge in said gaseous discharge device in response to Jtential applied to its in-put terminals; an impedance element; and switch`means for alternately .connecting said impedance ele- Vand second sections, said` first core section having a primarywinding positioned thereon adapted to be energized from a source of A. C. potential,

said second core section having a secondary Wind- .ing -thereon for supplying current to'a load circuit and said third core section having a control winding thereon, a control impedance, and means for connecting said control impedance in shunt to said control winding for controlling the current and potential delivered by said secondary Winding to the load. 4

'7. A system as described inclaim 6 in which said control impedance consists of a resistance element. '-l

8. A system as described in 'claim 6 in which said control impedance consists of reactance element.

9.0-A system as described in claim 6 in which said control impedance consists of a capacitative reactance element.

osMoN ERICKSON.

an inductive 

